feat: allow linking fediverse account to existing user

backend/db/user.go

@@ -31,6 +31,7 @@ type User struct {
 	Fediverse         *string
 	FediverseUsername *string
 	FediverseAppID    *int64
+	FediverseInstance *string
 
 	MaxInvites int
 
@@ -99,7 +100,8 @@ func (db *DB) CreateUser(ctx context.Context, tx pgx.Tx, username string) (u Use
 }
 
 func (db *DB) FediverseUser(ctx context.Context, userID string, instanceAppID int64) (u User, err error) {
-	sql, args, err := sq.Select("*").From("users").
+	sql, args, err := sq.Select("*", "(SELECT instance FROM fediverse_apps WHERE id = users.fediverse_app_id) AS fediverse_instance").
+		From("users").
 		Where("fediverse = ?", userID).Where("fediverse_app_id = ?", instanceAppID).
 		ToSql()
 	if err != nil {
@@ -141,7 +143,8 @@ func (u *User) UpdateFromFedi(ctx context.Context, ex Execer, userID, username s
 
 // DiscordUser fetches a user by Discord user ID.
 func (db *DB) DiscordUser(ctx context.Context, discordID string) (u User, err error) {
-	sql, args, err := sq.Select("*").From("users").Where("discord = ?", discordID).ToSql()
+	sql, args, err := sq.Select("*", "(SELECT instance FROM fediverse_apps WHERE id = users.fediverse_app_id) AS fediverse_instance").
+		From("users").Where("discord = ?", discordID).ToSql()
 	if err != nil {
 		return u, errors.Wrap(err, "building sql")
 	}
@@ -181,7 +184,8 @@ func (u *User) UpdateFromDiscord(ctx context.Context, ex Execer, du *discordgo.U
 
 // User gets a user by ID.
 func (db *DB) User(ctx context.Context, id xid.ID) (u User, err error) {
-	sql, args, err := sq.Select("*").From("users").Where("id = ?", id).ToSql()
+	sql, args, err := sq.Select("*", "(SELECT instance FROM fediverse_apps WHERE id = users.fediverse_app_id) AS fediverse_instance").
+		From("users").Where("id = ?", id).ToSql()
 	if err != nil {
 		return u, errors.Wrap(err, "building sql")
 	}

backend/routes/auth/discord.go

@@ -203,15 +203,15 @@ func (s *Server) discordSignup(w http.ResponseWriter, r *http.Request) error {
 
 	u, err := s.DB.CreateUser(ctx, tx, req.Username)
 	if err != nil {
+		if errors.Cause(err) == db.ErrUsernameTaken {
+			return server.APIError{Code: server.ErrUsernameTaken}
+		}
+
 		return errors.Wrap(err, "creating user")
 	}
 
 	err = u.UpdateFromDiscord(ctx, tx, du)
 	if err != nil {
-		if errors.Cause(err) == db.ErrUsernameTaken {
-			return server.APIError{Code: server.ErrUsernameTaken}
-		}
-
 		return errors.Wrap(err, "updating user from discord")
 	}
 

backend/routes/auth/fedi_mastodon.go

@@ -174,6 +174,57 @@ func (s *Server) mastodonCallback(w http.ResponseWriter, r *http.Request) error
 	return nil
 }
 
+type fediLinkRequest struct {
+	Instance string `json:"instance"`
+	Ticket   string `json:"ticket"`
+}
+
+func (s *Server) mastodonLink(w http.ResponseWriter, r *http.Request) error {
+	ctx := r.Context()
+
+	claims, _ := server.ClaimsFromContext(ctx)
+
+	req, err := Decode[fediLinkRequest](r)
+	if err != nil {
+		return server.APIError{Code: server.ErrBadRequest}
+	}
+
+	app, err := s.DB.FediverseApp(ctx, req.Instance)
+	if err != nil {
+		return errors.Wrap(err, "getting instance application")
+	}
+
+	u, err := s.DB.User(ctx, claims.UserID)
+	if err != nil {
+		return errors.Wrap(err, "getting user")
+	}
+
+	if u.Fediverse != nil {
+		return server.APIError{Code: server.ErrAlreadyLinked}
+	}
+
+	mu := new(partialMastodonAccount)
+	err = s.DB.GetJSON(ctx, "mastodon:"+req.Ticket, &mu)
+	if err != nil {
+		log.Errorf("getting mastoAPI user for ticket: %v", err)
+
+		return server.APIError{Code: server.ErrInvalidTicket}
+	}
+
+	err = u.UpdateFromFedi(ctx, s.DB, mu.ID, mu.Username, app.ID)
+	if err != nil {
+		return errors.Wrap(err, "updating user from mastoAPI")
+	}
+
+	fields, err := s.DB.UserFields(ctx, u.ID)
+	if err != nil {
+		return errors.Wrap(err, "getting user fields")
+	}
+
+	render.JSON(w, r, dbUserToUserResponse(u, fields))
+	return nil
+}
+
 type fediSignupRequest struct {
 	Instance   string `json:"instance"`
 	Ticket     string `json:"ticket"`
@@ -225,15 +276,15 @@ func (s *Server) mastodonSignup(w http.ResponseWriter, r *http.Request) error {
 
 	u, err := s.DB.CreateUser(ctx, tx, req.Username)
 	if err != nil {
+		if errors.Cause(err) == db.ErrUsernameTaken {
+			return server.APIError{Code: server.ErrUsernameTaken}
+		}
+
 		return errors.Wrap(err, "creating user")
 	}
 
 	err = u.UpdateFromFedi(ctx, tx, mu.ID, mu.Username, app.ID)
 	if err != nil {
-		if errors.Cause(err) == db.ErrUsernameTaken {
-			return server.APIError{Code: server.ErrUsernameTaken}
-		}
-
 		return errors.Wrap(err, "updating user from mastoAPI")
 	}
 

backend/routes/auth/routes.go

@@ -33,21 +33,28 @@ type userResponse struct {
 
 	Discord         *string `json:"discord"`
 	DiscordUsername *string `json:"discord_username"`
+
+	Fediverse         *string `json:"fediverse"`
+	FediverseUsername *string `json:"fediverse_username"`
+	FediverseInstance *string `json:"fediverse_instance"`
 }
 
 func dbUserToUserResponse(u db.User, fields []db.Field) *userResponse {
 	return &userResponse{
-		ID:              u.ID,
-		Username:        u.Username,
-		DisplayName:     u.DisplayName,
-		Bio:             u.Bio,
-		Avatar:          u.Avatar,
-		Links:           db.NotNull(u.Links),
-		Names:           db.NotNull(u.Names),
-		Pronouns:        db.NotNull(u.Pronouns),
-		Fields:          db.NotNull(fields),
-		Discord:         u.Discord,
-		DiscordUsername: u.DiscordUsername,
+		ID:                u.ID,
+		Username:          u.Username,
+		DisplayName:       u.DisplayName,
+		Bio:               u.Bio,
+		Avatar:            u.Avatar,
+		Links:             db.NotNull(u.Links),
+		Names:             db.NotNull(u.Names),
+		Pronouns:          db.NotNull(u.Pronouns),
+		Fields:            db.NotNull(fields),
+		Discord:           u.Discord,
+		DiscordUsername:   u.DiscordUsername,
+		Fediverse:         u.Fediverse,
+		FediverseUsername: u.FediverseUsername,
+		FediverseInstance: u.FediverseInstance,
 	}
 }
 
@@ -78,7 +85,7 @@ func Mount(srv *server.Server, r chi.Router) {
 		r.Route("/mastodon", func(r chi.Router) {
 			r.Post("/callback", server.WrapHandler(s.mastodonCallback))
 			r.Post("/signup", server.WrapHandler(s.mastodonSignup))
-			r.With(server.MustAuth).Post("/add-provider", server.WrapHandler(nil))
+			r.With(server.MustAuth).Post("/add-provider", server.WrapHandler(s.mastodonLink))
 		})
 
 		// invite routes

backend/routes/user/get_user.go

@@ -159,15 +159,6 @@ func (s *Server) getMeUser(w http.ResponseWriter, r *http.Request) error {
 		return err
 	}
 
-	// get fedi instance name if the user has a linked fedi account
-	var fediInstance *string
-	if u.FediverseAppID != nil {
-		app, err := s.DB.FediverseAppByID(ctx, *u.FediverseAppID)
-		if err == nil {
-			fediInstance = &app.Instance
-		}
-	}
-
 	render.JSON(w, r, GetMeResponse{
 		GetUserResponse:   dbUserToResponse(u, fields, members),
 		MaxInvites:        u.MaxInvites,
@@ -175,7 +166,7 @@ func (s *Server) getMeUser(w http.ResponseWriter, r *http.Request) error {
 		DiscordUsername:   u.DiscordUsername,
 		Fediverse:         u.Fediverse,
 		FediverseUsername: u.FediverseUsername,
-		FediverseInstance: fediInstance,
+		FediverseInstance: u.FediverseInstance,
 	})
 	return nil
 }

backend/server/errors.go

@@ -94,6 +94,7 @@ const (
 	ErrDeletionPending     = 1011 // own user deletion pending, returned with undo code
 	ErrRecentExport        = 1012 // latest export is too recent
 	ErrUnsupportedInstance = 1013 // unsupported fediverse software
+	ErrAlreadyLinked       = 1014 // user already has linked account of the same type
 
 	// User-related error codes
 	ErrUserNotFound = 2001
@@ -130,6 +131,7 @@ var errCodeMessages = map[int]string{
 	ErrDeletionPending:     "Your account is pending deletion",
 	ErrRecentExport:        "Your latest data export is less than 1 day old",
 	ErrUnsupportedInstance: "Unsupported instance software",
+	ErrAlreadyLinked:       "Your account is already linked to an account of this type",
 
 	ErrUserNotFound: "User not found",
 
@@ -163,6 +165,7 @@ var errCodeStatuses = map[int]int{
 	ErrDeletionPending:     http.StatusBadRequest,
 	ErrRecentExport:        http.StatusBadRequest,
 	ErrUnsupportedInstance: http.StatusBadRequest,
+	ErrAlreadyLinked:       http.StatusBadRequest,
 
 	ErrUserNotFound: http.StatusNotFound,
 

frontend/src/lib/api/entities.ts

@@ -21,6 +21,9 @@ export interface MeUser extends User {
   max_invites: number;
   discord: string | null;
   discord_username: string | null;
+  fediverse: string | null;
+  fediverse_username: string | null;
+  fediverse_instance: string | null;
 }
 
 export interface Field {

frontend/src/routes/auth/login/mastodon/[instance]/+page.svelte

@@ -4,10 +4,11 @@
 
   import { goto } from "$app/navigation";
   import type { APIError, MeUser } from "$lib/api/entities";
-  import { apiFetch } from "$lib/api/fetch";
+  import { apiFetch, apiFetchClient } from "$lib/api/fetch";
   import { userStore } from "$lib/store";
   import type { PageData } from "./$types";
   import ErrorAlert from "$lib/components/ErrorAlert.svelte";
+  import { addToast } from "$lib/toast";
 
   interface SignupResponse {
     user: MeUser;
@@ -67,6 +68,22 @@
       deleteError = e as APIError;
     }
   };
+
+  const linkAccount = async () => {
+    try {
+      const resp = await apiFetchClient<MeUser>("/auth/mastodon/add-provider", "POST", {
+        instance: data.instance,
+        ticket: data.ticket,
+      });
+
+      localStorage.setItem("pronouns-user", JSON.stringify(resp));
+      userStore.set(resp);
+      addToast({ header: "Linked account", body: "Successfully linked account!" });
+      goto("/settings/auth");
+    } catch (e) {
+      data.error = e as APIError;
+    }
+  };
 </script>
 
 <svelte:head>
@@ -78,7 +95,32 @@
 {#if data.error}
   <ErrorAlert error={data.error} />
 {/if}
-{#if data.ticket}
+{#if data.ticket && $userStore}
+  <div>
+    <label for="fediverse">Fediverse username</label>
+    <input
+      id="fediverse"
+      class="form-control"
+      name="fediverse"
+      readonly
+      value="{data.fediverse}@{data.instance}"
+    />
+  </div>
+  <div>
+    <label for="fediverse">pronouns.cc username</label>
+    <input
+      id="pronounscc"
+      class="form-control"
+      name="pronounscc"
+      readonly
+      value={$userStore.name}
+    />
+  </div>
+  <div>
+    <Button on:click={linkAccount}>Link account</Button>
+    <Button color="secondary" href="/settings/auth">Cancel</Button>
+  </div>
+{:else if data.ticket}
   <form on:submit|preventDefault={signupForm}>
     <div>
       <label for="fediverse">Fediverse username</label>
@@ -86,7 +128,7 @@
         id="fediverse"
         class="form-control"
         name="fediverse"
-        disabled
+        readonly
         value="{data.fediverse}@{data.instance}"
       />
     </div>

frontend/src/routes/settings/+layout.svelte

@@ -35,7 +35,14 @@
         <ListGroupItem tag="a" active={$page.url.pathname === "/settings"} href="/settings">
           Your profile
         </ListGroupItem>
-        {#if data.require_invite}
+        <ListGroupItem
+          tag="a"
+          active={$page.url.pathname === "/settings/auth"}
+          href="/settings/auth"
+        >
+          Authentication
+        </ListGroupItem>
+        {#if data.invitesEnabled}
           <ListGroupItem
             tag="a"
             active={$page.url.pathname === "/settings/invites"}

frontend/src/routes/settings/+layout.ts

@@ -1,8 +1,36 @@
+import {
+  ErrorCode,
+  type APIError,
+  type Invite,
+  type MeUser,
+  type PartialMember,
+} from "$lib/api/entities";
+import { apiFetchClient } from "$lib/api/fetch";
 import type { LayoutLoad } from "./$types";
 
 export const ssr = false;
 
 export const load = (async ({ parent }) => {
+  const user = await apiFetchClient<MeUser>("/users/@me");
+  const members = await apiFetchClient<PartialMember[]>("/users/@me/members");
+
+  let invites: Invite[] = [];
+  let invitesEnabled = true;
+  try {
+    invites = await apiFetchClient<Invite[]>("/auth/invites");
+  } catch (e) {
+    if ((e as APIError).code === ErrorCode.InvitesDisabled) {
+      invitesEnabled = false;
+    }
+  }
+
   const data = await parent();
-  return data;
+
+  return {
+    ...data,
+    user,
+    members,
+    invites,
+    invitesEnabled,
+  };
 }) satisfies LayoutLoad;

frontend/src/routes/settings/+page.ts

@@ -1,30 +0,0 @@
-import {
-  type Invite,
-  type APIError,
-  type MeUser,
-  type PartialMember,
-  ErrorCode,
-} from "$lib/api/entities";
-import { apiFetchClient } from "$lib/api/fetch";
-import { error } from "@sveltejs/kit";
-
-export const load = async () => {
-  try {
-    const user = await apiFetchClient<MeUser>("/users/@me");
-    const members = await apiFetchClient<PartialMember[]>("/users/@me/members");
-
-    let invites: Invite[] = [];
-    let invitesEnabled = true;
-    try {
-      invites = await apiFetchClient<Invite[]>("/auth/invites");
-    } catch (e) {
-      if ((e as APIError).code === ErrorCode.InvitesDisabled) {
-        invitesEnabled = false;
-      }
-    }
-
-    return { user, members, invites, invitesEnabled };
-  } catch (e) {
-    throw error(500, (e as APIError).message);
-  }
-};

frontend/src/routes/settings/auth/+page.svelte

@@ -0,0 +1,115 @@
+<script lang="ts">
+  import type { APIError } from "$lib/api/entities";
+  import { apiFetch } from "$lib/api/fetch";
+  import ErrorAlert from "$lib/components/ErrorAlert.svelte";
+  import {
+    Button,
+    Card,
+    CardBody,
+    CardText,
+    CardTitle,
+    Input,
+    Modal,
+    ModalBody,
+    ModalFooter,
+  } from "sveltestrap";
+  import type { PageData } from "./$types";
+
+  export let data: PageData;
+
+  let canUnlink = false;
+
+  $: canUnlink =
+    [data.user.discord, data.user.fediverse]
+      .map<number>((entry) => (entry === null ? 0 : 1))
+      .reduce((prev, current) => prev + current) >= 2;
+
+  let error: APIError | null = null;
+  let instance = "";
+  let fediDisabled = false;
+
+  let fediLinkModalOpen = false;
+  let toggleFediLinkModal = () => (fediLinkModalOpen = !fediLinkModalOpen);
+
+  const fediLogin = async () => {
+    fediDisabled = true;
+    try {
+      const resp = await apiFetch<{ url: string }>(
+        `/auth/urls/fediverse?instance=${encodeURIComponent(instance)}`,
+        {},
+      );
+      window.location.assign(resp.url);
+    } catch (e) {
+      error = e as APIError;
+    } finally {
+      fediDisabled = false;
+    }
+  };
+</script>
+
+<div>
+  <h1>Authentication providers</h1>
+
+  <div>
+    <div class="my-2">
+      <Card>
+        <CardBody>
+          <CardTitle>Fediverse</CardTitle>
+          <CardText>
+            {#if data.user.fediverse}
+              Your currently linked Fediverse account is <b
+                >{data.user.fediverse_username}@{data.user.fediverse_instance}</b
+              >
+              (<code>{data.user.fediverse}</code>).
+            {:else}
+              You do not have a linked Fediverse account.
+            {/if}
+          </CardText>
+          {#if data.user.fediverse}
+            <Button color="danger" disabled={!canUnlink}>Unlink account</Button>
+          {:else}
+            <Button color="secondary" on:click={toggleFediLinkModal}>Link account</Button>
+          {/if}
+        </CardBody>
+      </Card>
+    </div>
+    <div class="my-2">
+      <Card>
+        <CardBody>
+          <CardTitle>Discord</CardTitle>
+          <CardText>
+            {#if data.user.discord}
+              Your currently linked Discord account is <b>{data.user.discord_username}</b>
+              (<code>{data.user.discord}</code>).
+            {:else}
+              You do not have a linked Discord account.
+            {/if}
+          </CardText>
+          {#if data.user.discord}
+            <Button color="danger" disabled={!canUnlink}>Unlink account</Button>
+          {:else}
+            <Button color="secondary" href={data.urls.discord}>Link account</Button>
+          {/if}
+        </CardBody>
+      </Card>
+    </div>
+    <Modal header="Pick an instance" isOpen={fediLinkModalOpen} toggle={toggleFediLinkModal}>
+      <ModalBody>
+        <p>
+          <strong>Note:</strong> Misskey (and derivatives) are not supported yet, sorry.
+        </p>
+        <Input placeholder="Instance (e.g. mastodon.social)" bind:value={instance} />
+        {#if error}
+          <div class="mt-2">
+            <ErrorAlert {error} />
+          </div>
+        {/if}
+      </ModalBody>
+      <ModalFooter>
+        <Button color="primary" disabled={fediDisabled || instance === ""} on:click={fediLogin}
+          >Log in</Button
+        >
+      </ModalFooter>
+    </Modal>
+  </div>
+</div>

frontend/src/routes/settings/auth/+page.ts

@@ -0,0 +1,17 @@
+import { PUBLIC_BASE_URL } from "$env/static/public";
+import { apiFetch } from "$lib/api/fetch";
+
+export const load = async () => {
+  const resp = await apiFetch<UrlsResponse>("/auth/urls", {
+    method: "POST",
+    body: {
+      callback_domain: PUBLIC_BASE_URL,
+    },
+  });
+
+  return { urls: resp };
+};
+
+interface UrlsResponse {
+  discord: string;
+}

frontend/src/routes/settings/invites/+page.ts

@@ -1,25 +0,0 @@
-import { ErrorCode, type APIError, type Invite } from "$lib/api/entities";
-import { apiFetchClient } from "$lib/api/fetch";
-import { error } from "@sveltejs/kit";
-import type { PageLoad } from "../$types";
-
-export const load = (async () => {
-  const data = {
-    invitesEnabled: true,
-    invites: [] as Invite[],
-  };
-
-  try {
-    const invites = await apiFetchClient<Invite[]>("/auth/invites");
-    data.invites = invites;
-  } catch (e) {
-    if ((e as APIError).code === ErrorCode.InvitesDisabled) {
-      data.invitesEnabled = false;
-      data.invites = [];
-    } else {
-      throw error((e as APIError).code, (e as APIError).message);
-    }
-  }
-
-  return data;
-}) satisfies PageLoad;